TELEGRAPHIC APPARATUS. 
227 
A small commutator 0 , placed next the line, allows the latter 
to be put to earth in case of a storm, &c. 
The number of cells used for transmitting the signals varies 
according to the length of the cable. Between Marseilles and 
Malta, a distance of 834 miles, four or five cells are sufficient. 
* ! 
Electro -' Afmarls 
* vl. 
Ccmdensaieur 
(‘o'/g?maafy(ir 
n- 
C * 
y terro y 
?7/77777777777777077777m7777777’. 
Clef c/e 
transmission*. 
~ 1 1 
Pile 
1 — 
iHHHHbU 
Fig. T60, 
On the section between Malta and Alexandria, a distance of 
927 miles, eight or 10 cells are used. 
Three trough-cells are required to work the mouse-mill, and 
nine suffice to suitably magnetize the series of electro-magnets. 
The speed of transmission may reach 25 words per minute, 
and the signals are well formed and the apparatus is properly 
adjusted. It is easy to learn to read these signals, and the 
clerks acquire the power of doing so much quicker than when 
the mirror signals are used, which being transient and requir- 
